When Posting a Client to Office/Office to Client or Office receipt you can create a RIA (Receipt In Advance)
This is done by selecting the radio button when in the bills allocation screen to create a Receipt In Advance.
What will happen is this RIA will allocate automatically against subsequent bills that don't have an allocation already going against them at the point of the bill been done.
📌Note: If this RIA shouldn't be going against the newer bills, then this will need investigating by yourself as to what the original receipt should of gone against and correcting the ledger.